1. Field of the Invention
This invention concerns a sensitive J-tube instrument and a particular application thereof. More specifically it concerns an application of the principles involved to provide a novel manometer that has increased sensitivity. Also, a particular application is that of measuring the change in liquid level of a tank of liquid over a predetermined period of time, which change may indicate the presence of a leak.
2. Description of the Prior Art
The testing of underground tanks for leakage has always been a difficult problem. Heretofore, two known methods which have been used have had various drawbacks. A first method required the product to be removed from the tank and the vent lines to be sealed. Then the tank was pressurized with air to several pounds per square inch.The pressure would then be monitored over a given period of time for indications of a leak. Obvious drawbacks of that arrangement included the fact that changes in pressure indicated would not necessarily mean that the tank was leaking but it might just as well be in the connecting lines or dispensor from the tank. Furthermore, the removal of products from the tank was time consuming and costly, and the pressurizing of the tank risked damage thereto.
A second procedure which has been employed involved the fitting of the fill pipe of the tank with a four or five foot high standpipe, and then the tank would be filled with product to the top of the standpipe. Any leakage would then be detected by observing the drop in level of the standpipe. This method had a bad tendency to stress the tank and could expand the ends of the tank. Also, since product had to be added to the tank for this test the temperature would not be stable, and consequently considerable variations would have to be taken into consideration to make an accurate determination.
Consequently, it is an object of this invention to provide an instrument and/or method for determining leaks in large product tanks, such as underground storage tanks for gasoline or the like. It involves the principles of this invention which provides an amplification of the difference in surface levels of a pair of liquid columns that are connected by a U-tube.